using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Text;
using MesETL.App.Options;
using MesETL.Shared.Helper;
using Microsoft.Extensions.Options;
using MySqlConnector;

namespace MesETL.App.Services.Seq;

public class SeqService
{
    private readonly string _connectionString;
    private readonly Dictionary<SeqConfig, long> _cachedSequence;

    public IReadOnlyDictionary<SeqConfig, long> CachedSequence => _cachedSequence;

    public SeqService(IOptions<DatabaseOutputOptions> options)
    {
        var connStr = options.Value.ConnectionString ?? throw new ApplicationException("未配置输出数据库连接字符串");
        var builder = new MySqlConnectionStringBuilder(connStr)
        {
            Database = "mes_global"
        };
        _connectionString = builder.ConnectionString;

        _cachedSequence = new Dictionary<SeqConfig, long>();
    }

    private async Task<long> UpdateSequenceID(string name,int step,long max,bool recycle, int add)
    {
        var sql = new StringBuilder(
            $"""
            INSERT INTO seq (SeqName,CurrentVal,Increment,MinVal,MaxVal,UpdateTime)
            VALUES ({name},{add},{step},1,{max},NOW()) 
            ON DUPLICATE KEY UPDATE UpdateTime = NOW(),
            """);
        if (recycle)
        {
            sql.Append($"CurrentVal = (@updatedVal := IF(CurrentVal + {add} >= MaxVal, {add}, CurrentVal + {add}));");
        }
        else
        {
            sql.Append($"CurrentVal = (@updatedVal := CurrentVal + {add});");
        }
        sql.Append("SELECT @updatedVal;");
        var result = await DatabaseHelper.QueryScalarAsync(_connectionString, sql.ToString());
        return Convert.ToInt64(result);
    }

    public async Task<long> PeekKey(SeqConfig config)
    {
        var sql = $"SELECT CurrentVal FROM seq WHERE SeqName = '{config.Name}' LIMIT 1;";
        return Convert.ToInt64(await DatabaseHelper.QueryScalarAsync(_connectionString, sql));
    }
    
    public async Task<long[]> GetKeys(SeqConfig config, int count)
    {
        if (count < 1) return [];

        var list = new long[count];
        var add = config.Step * count;
        var lastId = await UpdateSequenceID(config.Name, config.Step, config.Max, config.Recycle, add);
        var step = Convert.ToInt64(config.Step);
        for (var i = count - 1; i > -1; i--)
        {
            list[i] = lastId;
            lastId -= step;
        }

        return list;
    }

    /// <summary>
    /// 添加并取得一个缓存的流水号
    /// </summary>
    /// <param name="config"></param>
    /// <returns></returns>
    public long AddCachedSeq(SeqConfig config)
    {
        if (!_cachedSequence.TryGetValue(config, out var val))
        {
            var seq = PeekKey(config).GetAwaiter().GetResult();
            val = seq;
            _cachedSequence[config] = val;
        }

        var step = config.Step;
        if (config.Recycle)
        {
            val = val + step >= config.Max ? val : val + step;
        }
        else val += step;
        _cachedSequence[config] = val;
        return val;
    }
    
    /// <summary>
    /// 移除一个缓存的流水号
    /// </summary>
    /// <param name="config"></param>
    public void RemoveCachedSeq(SeqConfig config)
    {
        _cachedSequence.Remove(config);
    }
    
    /// <summary>
    /// 清空所有缓存的流水号
    /// </summary>
    public void ClearCache()
    {
        _cachedSequence.Clear();
    }

    /// <summary>
    /// 将缓存的流水号应用至数据库
    /// </summary>
    public async Task ApplyToDatabaseAsync()
    {
        if (_cachedSequence.Count == 0) return;
        var sql = GenerateCachedSeqSql();
        await DatabaseHelper.NonQueryAsync(_connectionString, sql);
    }

    private string GenerateCachedSeqSql()
    {
        var sb = new StringBuilder();
        foreach (var kv in _cachedSequence)
        {
            sb.AppendLine($"UPDATE seq SET CurrentVal = {kv.Value} WHERE SeqName = '{kv.Key.Name}';");
        }

        return sb.ToString();
    }
}